In Singapore, Muslims and non-Muslims are subjected to different sets of inheritance law. Faraid is the Islamic law on inheritance and deals with how a deceased Muslim’s assets are distributed.
You are allowed to will away a maximum of 1/3 of your entire estate to non-Faraid beneficiaries (eg. illegitimate children, family members who are not Muslims, etc.). If you have a Muslim will (Wasiat), your executor (the person you appoint to distribute your assets) will need to go to court to get a grant of probate before distributing your assets according to your will. The rest will be distributed under the Faraid.
How your assets will be distributed under Faraid depends on your family composition. To get an absolute calculation of who will inherit your assets, you must get an Inheritance Certificate from the Syariah court.